(B) VITIATED INTENTION
The best example of a ground of restitution which operates where the claimant’s intention can be considered to be vitiated is mistake. Where the claimant transfers a benefit to the defendant as a result of an operative mistake, the claimant’s intention to transfer the benefit is considered to have been vitiated by virtue of the mistake.12 Similarly, where the claimant is compelled to transfer a benefit to the defendant, the claimant is not able to exercise a free choice by virtue of the compulsion, and so again his or her intention to transfer the benefit will be considered to have been vitiated.13
(C) QUALIFIED INTENTION
Where the claimant has transferred a benefit to the defendant on the basis that a condition will be satisfied, such as the receipt of a benefit in return, the claimant’s intention that the defendant should receive the benefit has been qualified. Consequently, if the condition fails, the claimant’s intention can be considered to have been negated by the failure and this will constitute the ground of restitution, which is called total failure of basis.
The crucial distinction between vitiated intention and qualified intention is that the claimant’s intention can only be vitiated by the circumstances which exist when the defendant received the benefit, whereas, where the claimant’s intention is qualified, the question of whether a ground of restitution can be established arises after the receipt of the benefit by the defendant.
-  See Chapter 13. 15 See Chapter 11. 16 See p 259, below.